Decompressing and Uploading Video to the net? How?

Whats the best way to decompress video (to make smaller file size) to put on the net. Some info would be extremely helpful. Well uploading them I assume is pretty easy. Any help especially with the compression question would be greatly appreciated?
Thanks

if you have PC use Dr.Divx also read about compressing from www.afterdawn.com you should learn how to use different bitrates, de-interlace etc. that you can get the best quality.
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Get a program that's called Cleaner (I think it's up to version 5 or 6) made by discreet. It's what all (and I mean all) effects and animation studios use as a compression tool. It has every codec available included with it or available to download for it. You can probably find it on Kazaa. My copy is bootleg, but it's for Mac. Works like a charm.